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Updated: Nov 4, 2025
Immunohistochemical Visualization of Hippocampal Neuron Activity After Spatial Learning in a Mouse Model of Neurodevelopmental Disorders
Published on: May 12, 2015
Evidence of hippocampal learning in human infants
Cameron T Ellis1, Lena J Skalaban1, Tristan S Yates1
1Department of Psychology, Yale University, 2 Hillhouse Avenue, New Haven, CT 06511, USA.
Insights
Infant hippocampus supports statistical learning by detecting regularities in visual sequences, even at 3 months old. This suggests early hippocampal function in learning environmental structure before episodic memory develops.
Area of Science:
- Neuroscience
- Developmental Psychology
- Cognitive Science
Background:
- The hippocampus is crucial for human memory, but its early functional development remains unclear.
- Infant memory development is slow, often attributed to an immature hippocampus.
- Direct functional testing of the infant hippocampus has been technically challenging.
Purpose of the Study:
- To test if the infant hippocampus supports statistical learning using task-based fMRI.
- To investigate the relationship between hippocampal development and statistical learning abilities in infants.
- To explore the role of different hippocampal subregions in early learning.
Main Methods:
- Utilized advanced task-based functional magnetic resonance imaging (fMRI) in awake human infants.
- Presented infants with visual sequences containing regularities and random patterns.
- Analyzed hippocampal and medial prefrontal cortex activity in relation to learning and age.
Main Results:
- Hippocampal activity increased when infants learned regularities in visual sequences compared to random ones.
- Learning-related hippocampal activity was present even in the youngest infants (around 3 months) and did not correlate with age.
- Statistical learning was more pronounced in the anterior than posterior hippocampus and also observed in the medial prefrontal cortex.
Conclusions:
- The infant hippocampus is functionally active for statistical learning from at least 3 months of age.
- This suggests the hippocampus supports learning environmental structure early in development, potentially before episodic memory formation.
- The findings highlight the hippocampus's role in extracting patterns from experience in early infancy.
Abstract:
The hippocampus is essential for human memory.1 The protracted maturation of memory capacities from infancy through early childhood2-4 is thus often attributed to hippocampal immaturity.5-7 The hippocampus of human infants has been characterized in terms of anatomy,8,9 but its function has never been tested directly because of technical challenges.10,11 Here, we use recently developed methods for task-based fMRI in awake human infants12 to test the hypothesis that the infant hippocampus supports statistical learning.13-15 Hippocampal activity increased with exposure to visual sequences of objects when the temporal order contained regularities to be learned, compared to when the order was random. Despite the hippocampus doubling in anatomical volume across infancy, learning-related functional activity bore no relationship to age. This suggests that the hippocampus is recruited for statistical learning at the youngest ages in our sample, around 3 months. Within the hippocampus, statistical learning was clearer in anterior than posterior divisions. This is consistent with the theory that statistical learning occurs in the monosynaptic pathway,16 which is more strongly represented in the anterior hippocampus.17,18 The monosynaptic pathway develops earlier than the trisynaptic pathway, which is linked to episodic memory,19,20 raising the possibility that the infant hippocampus participates in statistical learning before it forms durable memories. Beyond the hippocampus, the medial prefrontal cortex showed statistical learning, consistent with its role in adult memory integration21 and generalization.22 These results suggest that the hippocampus supports the vital ability of infants to extract the structure of their environment through experience.
